Good microbiological water quality in coastal waters is a national priority. With wastewater contaminating such aquatic areas, there is an increased risk of infection. The organisms responsible for infectious risk can include viruses, bacteria, and protozoans. Individuals at risk are those who have increased contact with contaminated water. These individuals nonexclusively include swimmers, divers, and boaters as well as those consuming products harvested from the contaminated water.
Pathogenic organisms such as enteric viruses pose a serious problem to life. Of the enteric viruses, one of the largest and best known groups is that of the enteroviruses, some of them important pathogens for humans and animals. Enteroviruses (EV) are small, non-enveloped, and isometric, belonging to the Picornaviridae family, and their genome consists of a simple chain RNA positive pole molecule (ssRNA+) with approximately 7,400 nucleotides (nt). These are the among the most common animal viruses and infect a large variety of mammals. The viruses are generally transmitted from person to person by ingestion (for example, fecal-oral route) or from exposure to contaminated water supplies. Furthermore, evidence indicates that the viruses can be spread via the respiratory tract. Once exposed, the virus infects the body via the blood stream and multiplies in the gut mucosa.
Approximately 90 serotypes of enteroviruses have been identified, 62 of which infect humans and 27 animals. Bovine enteroviruses (BEV) are broadly distributed all over the world and classified as enzootic in some countries. Two species have been described to date: BEV1 and BEV2 (Knowles, N. J., and Barnett, I. T. (1985), Arch Virol 83 (3-4), 141-55), although there are probably more that have not yet been identified. There are 3 species of porcine enteroviruses that have been described. An ovine enterovirus (OEV-1) that is closely linked to the BEVs has been isolated. The existence of viruses has been described in ocean environments, although it is believed that most of the viruses found in natural water are bacteriophages, cyanophages, and other types capable of infecting microalgae. The existence of water contaminated by human enteric viruses has also been described, especially close to urban areas, related to sources of human infections (Chapron et al., 2000, Appl. Environ. Microbiol. 66:2520-2525; Abbaszadegan et al., 1993, Appl. Environ. Microbiol. 59:1318-1324; Abbaszadegan et al., 1999, Appl. Environ. Microbiol. 65:444-449; Bosch A., 1998, Int. Microbiol. 1:191-196; Pianetti et al., 2000, Epidemiol. Infect. 125:455-462; Schvoerer et al., Res. Microbiol. 152:179-186).
Most infections occur during childhood. Although the infections are largely transient, they produce lifelong immunity to the organism. A majority of enteroviral infections result in mild illness; however, enteroviruses can cause an array of different diseases affecting many different organs (for example, neurologic (polio, aseptic meningitis, encephalitis), respiratory (common cold, tonsillitis, pharyngitis, rhinitis), cardiovascular (myocarditis, pericarditis), etc.). The ability to detect the presence of the organisms that cause these conditions is beneficial to the health and welfare of those with increased potential of exposure.
There is no specific treatment for enterovirus infections. In infants, enteroviral meningitis is often confused with bacterial or herpesvirus infections resulting in misdiagnosis. Often, children are hospitalized and incorrectly treated with antibiotics and anti-herpes drugs.
While most enteroviral infections are known and documented, these viruses have also been implicated in several chronic diseases, such as juvenile onset of diabetes mellitus, chronic fatigue syndrome, and amyotrophic lateral sclerosis (Lou Gehrig's Disease); however, definitive proof is deficient.
Furthermore, there is a high degree of serological cross reactivity amongst the more than 70 known enteroviruses, which include: Polio 1, 2, 3; Coxsackie A 1-24; Coxsackie B 1-6; ECHO 1-34; Entero 68-71; and Entero 72 (Hepatitis A). To reduce the risk of enteroviral infection, the U.S. EPA proposed legislation mandating the testing of groundwater for the presence of enteroviruses.
Noroviruses (genus Norovirus, family Caliciviridae) are a group of related, single-stranded RNA, non-enveloped viruses that cause acute gastroenteritis in humans. Norovirus was recently approved as the official genus name for the group of viruses provisionally described as “Norwalk-like viruses” (NLV). This group of viruses has also been referred to as caliciviruses (because of their virus family name) and as small round structured viruses, or SRSVs (because of their morphological features). Another genus of the calicivirus family that can cause gastroenteritis in humans is Sapovirus, formerly described as “Sapporo-like virus” (SLV) and sometimes referred to as classical or typical calicivirus.
Noroviruses are named after the original strain “Norwalk virus,” which caused an outbreak of gastroenteritis in a school in Norwalk, Ohio, in 1968. Currently, there are at least four norovirus genogroups (GI, GII, GIII, and GIV), which in turn are divided into at least 20 genetic clusters.
Noroviruses are transmitted primarily through the fecal-oral route, either by consumption of fecally contaminated food or water or by direct person-to-person contact. Environmental and fomite contamination may also act as a source of infection. Evidence exists for transmission due to aerosolization of vomitus that presumably results in droplets contaminating surfaces or entering the oral mucosa and being swallowed. Noroviruses are highly contagious, and it is thought that an inoculum bearing very few viral particles is sufficient to infect an individual. During outbreaks of norovirus gastroenteritis, several modes of transmission have been documented; for example, initial foodbome transmission in a restaurant, followed by secondary person-to-person transmission to household contacts. Although presymptomatic viral shedding may occur, shedding usually begins with onset of symptoms and may continue for 2 weeks after recovery.
The isolation and detection of such enteric pathogens is known to be accomplished by reverse transcriptase polymerase chain reaction (RT-PCR) and cell culture (See M. Gilgen et al., (1995) Appl. Environ. Microbiol. 61: 1226-31). Both of these techniques have advantages and disadvantages. While RT-PCR is generally faster, more sensitive, and more specific, it cannot distinguish viable from nonviable viruses. Further, currently available primer sets are not specific among the full suite of human enteroviruses. Currently only about 25 of the more than 70 known enteroviruses can be detected by the RT-PCR method. Thus, use of the RT-PCR assay allows sensitive detection but cannot determine whether the resulting amplicon is from one virus, multiple virus strains, a pathogen, or a vaccine.